Wants money for a contract that expired years ago

I took out a Cell C contract years ago. Still remember the girl that assisted me in Wesgate Mall. When I was supposed to sign the contract she said ag don't worry about reading the terms and conditions, just sign here which I did. I received a cell phone and I got airtime every month. When the 24 months were finished and I paid my last instalment, I never contacted them to renew my contract, didn't receive anymore airtime or a new free phone. Then years later I get a call saying I owe R800 because I didn't fax a letter saying that I want to cancel the contract. Are you kidding me? Years later, I received nothing to say that my contract is still open. Do they want me to pay money for no service, for free, mahala. Who in this day and age can give away free money. This is a disgusting and I will not be ********** like this.